We obtained some new Dell E7440 laptops with Intel dual band wireless-ac 7260 wireless cards installed. They would not connect to captive portal for guest access nor to any of our other SSID's using 802.1x. We got captive portal access by turning off band steering.

After further testing we were able to turn that back on on the controller and instead turn off the a band on the laptop. By default it is set to a/b/g and we set it to b/g to get it to connect. Notified Aruba of the issue as well.

Thought this post might help someone that tries using the same chipset and is unable to connect.

You might find you're hitting a similar issue to what I've posted about elsewhere. Granted, your adapter is different, but more or less all vendors make these kind of mistake in their haste to get products to market quickly.

I have spent time with Intel and Aruba on this as I'm experiencing the same issue. After about an hour of explaining to the Aruba guy that the problem wasn't related to enabling/disabling HT/VHT mode on the wifi card, and eventually being able to convince him that disabling the A radio enables connections to be made, we've got a call on hold to arrange for a time to do some further testing. Meanwhile, Dell have agreed to replace the wifi chip with a Broadcom one, since they seem to have experienced problems with the AC 7260. If I can get an agreed RMA date for them, I might not bother with further troubleshooting, but wanted to add my own experience to this thread in case others get the same issue.